1. What is the chemical formula for cholesterol?

• a) C27 H46 O

• b) C27 H45 OH

• c) C28 H47 OH

• d) C29 H48 O

• Answer: b) C27 H45 OH

2. What percentage of cholesterol in the body is derived from de novo biosynthesis?

• a) 20%

• b) 40%

• c) 70%

• d) 90%

• Answer: c) 70%

3. What is the main site of cholesterol synthesis?

• a) Intestine

• b) Adrenal cortex

• c) Liver

• d) Placenta

• Answer: c) Liver

4. What is the key intermediate in the cholesterol synthetic pathway?

• a) Acetyl-CoA

• b) Mevalonate

• c) Squalene

• d) Cholesterol

• Answer: b) Mevalonate

5. Which enzyme catalyzes the conversion of HMG-CoA to mevalonate?

• a) Acetyl-CoA synthetase

• b) Squalene synthase

• c) HMG-CoA reductase

• d) Alcohol dehydrogenase

• Answer: c) HMG-CoA reductase

6. What percentage of circulating cholesterol is in free form?

• a) 10%

• b) 20%

• c) 30%

• d) 50%

• Answer: c) 30%

7. Which enzyme esterifies cholesterol in plasma?

• a) ACAT

• b) LCAT

• c) HMG-CoA reductase

• d) Squalene synthase

• Answer: b) LCAT

8. What is the primary function of cholesterol in cell membranes?

• a) To increase fluidity

• b) To decrease fluidity

• c) To act as a precursor for steroid hormones

• d) To store energy

• Answer: b) To decrease fluidity

9. Which lipoprotein is responsible for reverse cholesterol transport?

• a) LDL

• b) VLDL

• c) HDL

• d) Chylomicrons

• Answer: c) HDL

10. What is the primary storage form of cholesterol in cells?

• a) Free cholesterol

• b) Cholesteryl ester

• c) Squalene

• d) Mevalonate

• Answer: b) Cholesteryl ester

11. What genetic disorder is characterized by high levels of LDL-bound cholesterol?

• a) Diabetes mellitus

• b) Familial hypercholesterolemia

• c) Phenylketonuria

• d) Sickle cell anemia

• Answer: b) Familial hypercholesterolemia

12. What is the function of the SREBP:SCAP complex when intracellular cholesterol is low?

• a) Decreases HMG-CoA reductase activity

• b) Increases HMG-CoA reductase activity

• c) Transports cholesterol out of the cell

• d) Esterifies cholesterol

• Answer: b) Increases HMG-CoA reductase activity

13. Which enzyme is responsible for converting squalene to cholesterol?

• a) Squalene synthase

• b) Squalene cyclase

• c) HMG-CoA reductase

• d) Acetyl-CoA synthetase

• Answer: b) Squalene cyclase

14. What is a major regulatory enzyme of cholesterol synthesis?

• a) LCAT

• b) ACAT

• c) HMG-CoA reductase

• d) Squalene synthase

• Answer: c) HMG-CoA reductase

15. What is the consequence of HMG-CoA reductase inhibition by statins?

• a) Decreased LDL receptor production

• b) Increased cholesterol synthesis

• c) Increased utilization of LDL reserves

• d) Decreased plasma levels of HDL

• Answer: c) Increased utilization of LDL reserves

16. How is excess intracellular free cholesterol regulated?

• a) By converting it to bile acids

• b) By converting it to cholesteryl ester

• c) By excreting it in urine

• d) By storing it in the mitochondria

• Answer: b) By converting it to cholesteryl ester

17. What is the primary route of cholesterol excretion?

• a) Urine

• b) Sweat

• c) Feces

• d) Breath

• Answer: c) Feces

18. Which disease is characterized by mutations in the gene encoding 7-dehydrocholesterol reductase?

• a) Smith-Lemli-Opitz syndrome

• b) Familial hypercholesterolemia

• c) Lathosterolosis

• d) Hepatic steatosis

• Answer: a) Smith-Lemli-Opitz syndrome

19. What role does cholesterol play in nerve conduction?

• a) Acts as a neurotransmitter

• b) Provides insulation to nerve fibers

• c) Increases synaptic transmission speed

• d) Decreases synaptic transmission speed

• Answer: b) Provides insulation to nerve fibers

20. What percentage of cholesterol is excreted after conversion to bile acids?

• a) 20%

• b) 30%

• c) 50%

• d) 70%

• Answer: c) 50%